written by: Leigh A. Zaykoski•edited by: Leigh A. Zaykoski•updated: 2/28/2010
Endocrinology is the branch of medicine that deals with the glands and hormones of the human body. Doctors in this specialty use a number of endocrinology blood tests to identify hormone imbalances and abnormal gland function.
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Pituitary Hormone Tests
The pituitary gland, also known as the “master gland" of the human body, produces hormones that control many of the body’s functions. Overproduction or underproduction of these hormones results in hormonal imbalances and other serious effects. The pituitary gland produces human growth hormone, thyroid stimulating hormone, luteinizing hormone, follicle stimulating hormone, adrenocorticotropic hormone, prolactin, and vasopressin. These hormones serve several important functions.
Growth Hormone: This hormone regulates growth in the human body.
Thyroid Stimulating Hormone: Thyroid stimulating hormone stimulates the thyroid gland to produce thyroid hormones and controls the core temperature of the body.
Luteinizing Hormone and Follicle Stimulating Hormones: These hormones play a role in reproduction.
Adrenocorticotropic Hormone (ACTH): ACTH plays a role in the release of adrenal gland hormones.
Prolactin: This hormone stimulates the production of breast milk.
Vasopressin: Vasopressin controls the retention of water in the body.
Endocrinologists check levels of these hormones when they suspect pituitary dysfunction. Abnormal pituitary hormone levels may indicate pituitary tumors, pituitary failure, Cushing’s disease, cysts, and other endocrine conditions.
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Thyroid Function Tests
The thyroid gland controls metabolism, energy, calcium levels, hormones, oxygen, weight loss, and excess fats in the body. This gland produces T3 and T4, two hormones that assist in the regulation of these functions. Doctors test the production of T3, T4, and thyroid binding globulin to determine if the thyroid gland is working properly.
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Glucose Tolerance Tests
Since the endocrine system affects the way the body metabolizes glucose, endocrinologists often order the glucose tolerance test. One of the most common forms of this test is the oral tolerance test. You must fast after midnight on the night before you go for the test. During the test, you will have to drink a liquid that contains a specific amount of glucose. A phlebotomist will draw your blood before the test to determine your glucose level before you drink the glucose solution. During the test, the phlebotomist will take more blood every 30 to 60 minutes.
The National Institutes of Health reports that normal glucose levels during this test are as follows:
Pre-test: 60 to 100 mg/dL
After one hour: less than 200 mg/dL
After two hours: less than 140 mg/dL
If your blood glucose is 140 to 200 mg/dL after two hours, you have an increased risk for diabetes. This is also known as pre-diabetes. Glucose levels of above 200 mg/dL after two hours indicate diabetes mellitus, or type 2 diabetes.
Risks of this test include fainting, bleeding, bruising, infection, and lightheadedness. Test results can be altered by several factors. These factors include vigorous exercise, stress from surgery, infection, and use of certain medications. Medications that alter the results of the glucose tolerance test include psychiatric medications, beta-blockers (used for high blood pressure and anxiety treatment), birth control pills, corticosteroids, and some diuretics.